Gastroesophageal Reflux Disease (GERD)
Orally administered famotidine was compared to placebo in a U.S. study that enrolled patients with symptoms of GERD and without endoscopic evidence of erosion or ulceration of the esophagus. Famotidine 20 mg b.i.d. was statistically significantly superior to 40 mg h.s. and to placebo in providing a successful symptomatic outcome, defined as moderate or excellent improvement of symptoms (Table 3).
†† p ≤0.01 vs Placebo
|Table 3 % Successful Symptomatic Outcome|
|Famotidine 20 mg b.i.d. (N=154)||Famotidine 40 mg h.s. (N=149)||Placebo (N=73)|
Symptomatic improvement and healing of endoscopically verified erosion and ulceration were studied in two additional trials. Healing was defined as complete resolution of all erosions or ulcerations visible with endoscopy. The U.S. study comparing famotidine 40 mg p.o. b.i.d. to placebo and famotidine 20 mg p.o.b.i.d. showed a significantly greater percentage of healing for famotidine 40 mg b.i.d. at weeks 6 and 12 (Table 4).
††† p ≤0.01 vs Placebo
‡ p ≤0.05 vs Famotidine 20 mg b.i.d.
‡‡ p ≤0.01 vs Famotidine 20 mg b.i.d.
|Table 4 % Endoscopic Healing — U.S. Study|
|Famotidine 40 mg b.i.d. (N=127)||Famotidine 20 mg b.i.d. (N=125)||Placebo (N=66)|
|Week 6 Week 12||48†††, ‡‡ 69†††, ‡||32 54†††||18 29|
As compared to placebo, patients who received famotidine had faster relief of daytime and nighttime heartburn and a greater percentage of patients experienced complete relief of nighttime heartburn. These differences were statistically significant.
In the international study, when famotidine 40 mg p.o. b.i.d. Was compared to ranitidine 150 mg p.o. b.i.d., a statistically significantly greater percentage of healing was observed with famotidine 40 mg b.i.d. at week 12 (Table 5). There was, however, no significant difference among treatments in symptom relief.
‡‡‡ p ≤0.05 vs Ranitidine 150 mg b.i.d.
|Table 5 % Endoscopic Healing — International Study|
|Famotidine 40 mg b.i.d. (N=175)||Famotidine 20 mg b.i.d. (N=93)||Ranitidine 150 mg b.i.d. (N=172)|
|Week 6 Week 12||48 71‡‡‡||52 68||42 60|
In studies of patients with pathological hypersecretory conditions such as Zollinger-Ellison Syndrome with or without multiple endocrine adenomas, famotidine significantly inhibited gastric acid secretion and controlled associated symptoms. Orally administered doses from 20 to 160 mg q 6 h maintained basal acid secretion below 10 mEq/hr; initial doses were titrated to the individual patient need and subsequent adjustments were necessary with time in some patients. Famotidine was well tolerated at these high dose levels for prolonged periods (greater than 12 months) in eight patients, and there were no cases reported of gynecomastia, increased prolactin levels, or impotence which were considered to be due to the drug.
Table 6 presents pharmacokinetic data from clinical trials and a published study in pediatric patients (<1 year of age; N=27) given famotidine I.V. 0.5 mg/kg and from published studies of small numbers of pediatric patients (1-15 years of age) given famotidine intravenously. Areas under the curve (AUCs) are normalized to a dose of 0.5 mg/kg l.V. for pediatric patients 1-15 years of age and compared with an extrapolated 40 mg intravenous dose in adults (extrapolation based on results obtained with a 20 mg I.V. adult dose).
a Values are presented as means ± SD unless indicated otherwise.
b Mean value only.
c Single center study.
d Multicenter study.
|Table 6 Pharmacokinetic Parametersa of Intravenous Famotidine|
|Age (N=number of patients)||Area Under the Curve (AUC) (ng-hr/mL)||Total Clearance (Cl) (L/hr/kg)||Volume of Distribution (Vd ) (L/kg)||Elimination Half-life (T1/2 ) (hours)|
|0-1 monthc (N=10)||NA||0.13 ± 0.06||1.4 ± 0.4||10.5 ± 5.4|
|0-3 monthsd (N=6)||2688 ± 847||0.21 ± 0.06||1.8 ± 0.3||8.1 ± 3.5|
|>3-12 monthsd (N=11)||1160 ± 474||0.49 ± 0.17||2.3 ± 0.7||4.5 ± 1.1|
|1-11 yrs (N=20)||1089 ± 834||0.54 ± 0.34||2.07 ± 1.49||3.38 ± 2.60|
|11-15 yrs (N=6)||1140 ± 320||0.48 ± 0.14||1.5 ± 0.4||2.3 ± 0.4|
|Adult (N=16)||1726b||0.39 ± 0.14||1.3 ± 0.2||2.83 ± 0.99|
Plasma clearance is reduced and elimination half-life is prolonged in pediatric patients 0-3 months of age compared to older pediatric patients. The pharmacokinetic parameters for pediatric patients, ages >3 months-15 years, are comparable to those obtained for adults.
Bioavailability studies of 8 pediatric patients (11-15 years of age) showed a mean oral bioavailability of 0.5 compared to adult values of 0.42 to 0.49. Oral doses of 0.5 mg/kg achieved AUCs of 645 ( 249 ng-hr/mL and 580 ( 60 ng-hr/mL in pediatric patients <1 year of age (N=5) and in pediatric patients 11-15 years of age, respectively, compared to 482 ( 181 ng-hr/mL in adults treated with 40 mg orally.
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